Chapter 19: Q19P (page 488)

Explain what is done in flow injection analysis and sequential injection. What is the principal difference between the two techniques? Which one is called “lab-on-a-valve”?

Short Answer

Expert verified

It is called “ lab-on- a valve because sample, reagents, and product all flow through a central multiport valve.

Step by step solution

Step1:

In flow injection analysis, a sample is injected into a continuously flowing liquid carrier containing a reagent that reacts with the sample. More reagents can be added further downstream. As sample and reagents flow from the injector to the detector, they react with each other to form a product. Detector measures property (absorbance) of the flowing stream.

Step 2:

In sequential injection, sample and reagents are sequentially injected into a holding coil. Then the six-way valve is rotated to take reagent from port 3 into the holding coil. Flow is then stopped to allow sample and reagent to mix and react in the holding coil. After a time, flow is reversed and the mixture is directed via port 2 through the detector (absorbance is measured at a selected wavelength). Volumes of each reagent and time in the mixing coil are under computer control.

Step 3:

The principal difference between the two techniques is that in sequential injection flow is not continuous and smaller volumes of reagents are required and less waste is generated than in flow injection. Flow injection uses continuous flow. Sequential injection is called "lab-on-a-valve" because sample, reagents, and product all flow through a central multiport valve.